One of the central aims of vision research is to elucidate the molecular changes photoreceptor membrane undergoes during bleaching. While a variety of biophysical methods have been developed which are capable of probing rhodopsin structure, only in special cases can specific information be obtained about individual molecular groups. We have recently demonstrated that Fourier transform infrared (FTIR) difference spectroscopy can detect and characterize single group alterations inside intact photoreceptor membrane during each step in the bleaching sequence. We now propose to utilize this new method in combination with a variety of biochemical and molecular genetic techniques to more fully elucidate how photoreceptor membrane functions. This includes rhodopsin regeneration with specifically labelled retinals, reconstitution with various lipids and site-specific mutation of individual amino acids in the rhodopsin sequence. The development of such a combined spectroscopic and biochemical approach should also help provide a general method for studying other membrane based systems.